The keyboard in a computer system is a device for data input, which consists of a set of keys. Once either key is pressed, a specific circuit is connected to produce a specific input signal. Regular computer keyboards may be gathered into two groups, one is the mechanical type and the other is the membrane type. In a mechanical keyboard, the keys can be conveniently arranged according to the layout of the printed circuit board. As illustrated in FIG. 1, the two pins of the key switch are inserted through holes on the printed circuit board and welded in place. This mechanical key switch is expensive to manufacture and simultaneously increases the total thickness of a keyboard. Furthermore, this mechanical key switch may be damaged easily because it is to trigger a signal by striking.
FIG. 2 illustrates a membrane key switch according to the prior art, in which a support is formed on a frame above a membrane and a plate to support a key cap by a rubber base plate permitting the plunger of the key cap to insert through a hole the frame. This arrangement greatly reduces the total thickness of a keyboard. However, because the post is directly formed on the frame, precision is very critical. Once the layout is fixed, the arrangement of the key switches on a keyboard can no longer be changed. Therefore, the tooling charge for a membrane keyboard is very expensive, and high risk is involved in making a mold according to the desired layout. This type of membrane keyboards are commonly used for notebook computers.